Solid state radio frequency (RF) switches are important components of Radar transmit/receive (T/R) modules, satellite communication systems, Joint Tactical Radio Systems (JTRS), and the like. A promising RF switch technology uses Heterostructure Field Effect Transistors (HFETs). Recently, high power switches made of AlGaN/GaN HFETs demonstrated superior performance over other RF switching devices in terms of maximum power density, bandwidth, operating temperature, and breakdown voltage.
Many applications, including JTRS and low-noise receivers, require RF switches with a very low insertion loss, e.g., typically below 0.3 dB. A low loss switch dissipates little RF power. As a result, the switch can be fabricated over a low cost substrate, such as sapphire. Low insertion loss in an HFET is due to a high channel conductance of the device. Exceptionally high two dimensional electron gas densities at the AlGaN/GaN interface make a group III-Nitride HFET an ideal candidate for RF switching applications.
The feasibility of high-power broad-band monolithically integrated group III-Nitride HFET RF switches has been demonstrated. Large signal analysis and experimental data for a large periphery group III-Nitride switch indicate that the switch can achieve switching powers exceeding +40 to +50 dBm. To date, the performance of any FET-based RF switch is limited by a trade off between a reasonably low threshold voltage versus low OFF state capacitances, high switching powers, and high linearity.